Will be interesting to see how this unfolds.
Blades
When it comes to offshore wind power, bigger really is better. The energy captured from the wind is determined by the swept area of the blades, an area which is proportional to the square of the blade length. Doubling the blade length quadruples the energy capture. There is therefore an incentive to have fewer, larger turbines that cost less overall to install and maintain than a higher number of smaller installations. However, with increasing blade length, the thickness and width of the blade also tend to increase, with concomitant increase in the blade mass. Innovations in design and materials have been able to significantly reduce blade mass whilst allowing for longer blades which maintain a high stiffness.
Composite materials made from polymer resins reinforced with fibrous materials have been used to provide a balance between high stiffness and low weight such that blade size can be maximised. The mechanical properties (e.g. stiffness) of fibre-reinforced composites are, at least in part, determined by the identity and volume content of the fibres. Whilst traditional composites comprised borosilicate glass fibres, recent developments in fibre technology have seen carbon, basalt, aramid and even natural fibres incorporated into the composites used in turbine blades. Mixtures of different fibres and/or secondary reinforcements such as carbon nanotubes, graphene, or nanoclays, have also been combined to make hybrid composites, which achieve a balance of desirable properties, including stiffness, damage tolerance, compressive strength, and polymer resin adhesion. Hybrid materials enable increasingly longer blades to be achieved, the longest wind turbine blade currently in service being GE Renewable Energy’s 107m long blade, made from a composite comprising glass and carbon fibers, and wood, fused together in a polymeric resin.
As blades get longer, the amount of material they contain increases and the tolerance for manufacturing defects or errors decreases. Improvements in manufacturing methods help maintain quality and consistency as turbine blades increase in size. A turbine blade typically comprises two faces (aeroshells) joined together with either one or more integral webs linking the upper and lower parts of the blade shell, or a box beam. Aeroshells can be made using “prepreg” technology, adapted from the aviation industry, wherein pre-impregnated composite fibres containing an amount of matrix material bonding them together are formed into the required shape. Alternatively, aeroshells can be made using resin infusion technology, in which fibres are unidirectionally orientated in a mould with polymer foams or balsa wood forming the sandwich structure before injecting a resin into the mould cavity, for example under vacuum, and curing. The challenges faced in comparison with the manufacture of composite structures for aerospace are in making blades with much larger thicknesses and larger amounts of materials.
The important question for innovators is, as ever, how best to protect these new materials and manufacturing methods? The prior art landscape in this area is congested, since the materials and methods used in making offshore wind turbines are frequently used in other industries such as aerospace or conventional power generation. In order to distinguish over the prior art and obtain patent protection, specific structural and compositional characteristics must be clearly defined and claimed. For example, definition of the properties of the composite, the reinforcing fibres, and/or the resin material may be required, including tensile strength and modulus, fibre length, additive particle size, and molecular weight of the resin. When drafting applications including such parameters, it is important to be aware of the requirements for ensuring the invention is clearly and sufficiently disclosed. The European Patent Office, for example, is strict on the examination of the clarity and sufficiency of claims including parameters and sets clear guidelines for patentability. Applicants need to be aware at the outset how to define the characteristics of these materials and methods in a way which is acceptable to the patent offices of the countries in which protection is desired in order to avoid pitfalls in the patent application process.